Postoperative analgesic effects of various quadratus lumborum block approaches following cesarean section: a randomized controlled trial

PURPOSE: Quadratus lumborum block (QLB) is shown to be effective on analgesia following cesarean section. This study aimed to compare the effects of three practical QLB approaches and classic epidural analgesia (EA) for cesarean section under spinal anesthesia. PATIENTS AND METHODS: Parturients undergoing elective cesarean section were randomized as group 1 (QLB type 2), group 2 (QLB type 3), group 3 (QLB type 2+3) and group 4 (EA). The block was performed at the end of the operation, and the epidural group was given a single epidural bolus. All subjects were provided with intravenous patient-controlled analgesia under identical settings. In addition, the postoperative pain severity was assessed by the VAS, which together with the morphine consumption at specific time intervals, was recorded within 48 hrs after surgery. Data were collected from December 2017 to June 2018. RESULTS: A total of 94 parturients had completed the study. At almost all postoperative time points, the VAS scores at rest and with movement in QLB type 2+3 group were lower than those in QLB type 2 or 3 group. The mean additional morphine consumption in QLB type 2+3 group (2.7 mg) was lower than that in QLB type 2 or 3 group (6.1 mg and 5.7 mg, respectively) within 48 h after surgery (P<0.001). Besides, the total morphine consumption in EA group (1.3 mg) was lower than that in any other QLB group (P<0.001). CONCLUSIONS: The analgesic effect of QLB is highly dependent on the injection position of local anesthetic. Besides, the ultrasound-guided QLB type 2+3 can provide superior analgesic effect following cesarean section to that of QLB type 2 or 3 block. However, it remains to be further validated about whether the combination of QLB type 2 and 3 is the best approach.